Final answer:
After an elastic collision, where cart B loses velocity and cart A begins moving, if both carts were identical and made of the same material, cart A could not be hollow. On a frictionless track, more information is needed to determine whether the carts are identical or if their masses differ.
Therefore the correct answer is option D. More information is needed./None of the above.
Step-by-step explanation:
Considering two carts, A and B, on a frictionless track where cart B is given a constant velocity and collides elastically with cart A, it is observed that after the collision, both carts move to the right with B moving slower than before. This situation implies that some of B's momentum has been transferred to A, resulting in both moving in the same direction post-collision. Since both carts are said to be made of the same material and look identical, but B lost some velocity and A gained velocity, we can infer that the mass of A must be greater than or equal to the mass of B for it to move after being initially at rest.
If the mass of A were less than B, then after an elastic collision, B would likely continue moving right with less reduction in its velocity, and A would move right faster than B. In an elastic collision, the total kinetic energy is conserved, and the only way B would lose velocity while transferring enough motion to get A moving is if A has more mass (indicating it is not hollow) or equal mass to B. Therefore, the conclusion cannot be that A is hollow (a), nor that B is hollow (c). If they are identical (b), they would have the same mass, which could be a possibility if they move at the same speed after the collision, but this is not the case. Without knowing the relative masses, the decision between (b) and (d) cannot be made, so more information is needed (d) to make an accurate conclusion.